Material with pH not higher than 7 containing silver halide, reducing agent and polymerizable compound

ABSTRACT

A light-sensitive material comprising a light-sensitive layer which contains silver halide, a reducing agent and a polymerizable compound provided on a support, characterized in that the light-sensitive layer has a pH value of not higher than 7.

BACKGROUND OF THE INVENTION 1. Field of the invention

This invention relates to a light-sensitive material comprising alight-sensitive layer containing silver halide, a reducing agent and apolymerizable compound provided on a support. 2. Description of priorart

Light-sensitive materials comprising a light-sensitive layer containingsilver halide, a reducing agent and a polymerizable compound provided ona support can be used in an image forming method in which a latent imageof silver halide is formed, and then the polymerizable compound ispolymerized to form the corresponding image.

Examples of said image forming methods are described in Japanese PatentPublication Nos. 45(1970)-11149 (corresponding to U.S. Pat. No.3,697,275), 47(1972)-20741 (corresponding to U.S. Pat. No. 3,687,667)and 49(1974) -10697, and Japanese Patent Provisional Publication Nos.57(1982)-138632, 57(1982)-142638, 57(1982)-176033, 57(1982)-211146(corresponding to U.S. Pat. No. 4,557,997), 58(1983)-107529(corresponding to U.S. Pat. No. 4,560,637), 58(1983)-121031(corresponding to U.S. Pat. No. 4,547,450) and 58(1983)-169143. In theseimage forming methods, when the exposed silver halide is developed usinga developing solution, the polymerizable compound is induced topolymerize in the presence of a reducing agent (which is oxidized) toform a polymer image. Thus, these methods need a wet development processemploying a developing solution. Therefore the process takes arelatively long time for the operation.

An improved image forming method employing a dry process is described inJapanese Patent Provisional Publication Nos. 61(1986)-69062 and61(1986)-73145 (the contents of both publications are described in U.S.Pat. No. 4,629,676 and European Patent Provisional Publication No.0174634A2). In this image forming method, a recording material (i.e.,light-sensitive material) comprising a light-sensitive layer containinga light-sensitive silver salt (i.e., silver halide), a reducing agent, across-linkable compound (i.e., polymerizable compound) and a binderprovided on a support is imagewise exposed to form a latent image, andthen the material is heated to form a polymer within the area where thelatent image of the silver halide has been formed. The above methodemploying the dry process and the light-sensitive material employablefor such method are also described in Japanese Patent ProvisionalPublication Nos. 61(1986)-183640, 61(1986)-188535 and 61(1986)-228441.

The above-mentioned image forming methods are based on the principle inwhich the polymerizable compound is polymerized within the area where alatent image of the silver halide has been formed.

Japanese Patent Provisional Publication No. 61(1986) -260241(corresponding to U.S. patent application Ser. No. 854,640) describesanother image forming method in which the polymerizable compound withinthe area where a latent image of the silver halide has not been formedis polymerized. In this method, when the material is heated, thereducing agent functions as polymerization inhibitor within the areawhere a latent image of the silver halide has been formed, and thepolymerizable compound within the other area is polymerized.

SUMMARY OF THE INVENTION

The present inventor has found that the sensitivity of a light-sensitivematerial employed in the above mentioned image-forming methods and thesharpness of the obtained image tend to lower while the material ispreserved under severe conditions.

An object of the present invention is to provided a light-sensitivematerial which is improved in the preservability.

There is provided by the present invention a light-sensitive materialcomprising a light-sensitive layer which contains silver halide, areducing agent and a polymerizable compound provided on a support,characterized in that the light-sensitive layer has a pH value of nothigher than 7.

The present inventor has noted that the light-sensitive materialsdisclosed in the above-mentioned publications are apt to lower in thesensitivity when these are stored for a long period of time or undersevere conditions such as at a high temperature and high humidity andfurther tend to give an image of lowered sharpness after stored for along period of time or under severe conditions. As a further study ofthe known light-sensitive material, the inventor has discovered that thepH conditions of the light-sensitive layers of the known light-sensitivematerials adversely influence the preservability of the material. Inmore detail, the pH value of the light-sensitive layers of the knownlight-sensitive materials are set to such a high value, higher than 7,because the development of the light-sensitive layer proceeds smoothlyat such a high pH value. According to the study of the present inventor,such high pH value adversely influences the preservability of thelight-sensitive material.

The pH value of the light-sensitive layer of the light-sensitivematerial of the invention can be enhanced at the time of development orin advance of the time of development in an appropriate way.

Therefore, the light-sensitive material of the invention can give animproved clear image, even if the material is preserved for a long termor under severe conditions.

DETAILED DESCRIPTION OF THE INVENTION

The light-sensitive layer of the light-sensitive material of theinvention has a pH value of not higher than 7. The light-sensitive layerpreferably has a pH value of not higher than 6.5.

The pH value of the light-sensitive layer preferably is higher than 7 ina development process. When the pH value of the light-sensitive layer istoo low, it is difficult to process or to construct the light-sensitivematerial for raising the pH value of the light-sensitive layer. Further,the preservability of the light-sensitive material is not so improved asexpected, when the pH value is lower than 5. Therefore, thelight-sensitive layer preferably has a pH value of not lower than 5.

In the present invention, the pH value of the light-sensitive layermeans a value obtained by a process comprising: dropping distilled wateron the light-sensitive layer; placing a glass electrode of a pH meter onthe area wetted by the distilled water on the light-sensitive layer toconnect the glass electrode with the layer via water; and measuring thevalue after lapse of 30 seconds.

In the case that the light-sensitive layer contains microcapsules, thereducing agent has remarkably deteriorated when the light-sensitivelayer has a pH value of higher than 7. Therefore, the light-sensitivematerial of the invention is more advantageous in an embodiment in whichthe light-sensitive layer contains microcapsules. The above effect isobserved whether the reducing agent is contained in the microcapsule,arranged outside of the microcapsule, or contained in the shell materialof the microcapsule.

There is no specific limitation with respect to the preparation of thelight-sensitive layer having the pH value of not higher than 7. The pHvalue of the light-sensitive layer is easily and preferably adjusted atthe stage of the coating solution of the light-sensitive layer in theprocess for the preparation of the light-sensitive material. Forinstance, an acid is added to the coating solution for lowering the pHvalue of the solution. There is also no specific limitation with respectto the acid, and either an inorganic acid, an organic acid or an acidicsalt can be employed. Among these acids, an acid such as sulfuric acidor nitric acid which is unreactive to silver for the formation of acomplex salt is preferred. Further, an acid having such a property thatit can be vaporized or decomposed in the development process is alsopreferred. For example, in the case that heat development is utilizedfor developing the light-sensitive material, an acid such as acetic acidwhich is vaporized or decomposed when it is heated (generally at 80° to200° C.) can be used. These acids can be used singly or in combination.

As mentioned before, the pH value of the light-sensitive layerpreferably is higher than 7 in the development process. Therefore, thelight-sensitive material of the invention is preferably treated forraising the pH value of the light-sensitive layer in the image-formingmethod simultaneously with or prior to the development process.Alternatively, the light-sensitive material of the can be so constructedthat the pH value of the light-sensitive layer rises by itself in thedevelopment process.

The process for raising the pH value of the light-sensitive layer isdescribed below.

Where the development is conducted using a developing solution in thesame manner as the image-forming method described in Japanese PatentPublication No. 45(1970)-11149 (corresponding to U.S. Pat. No.3,697,275), a base can be previously contained in the developingsolution.

Where the development is heat development in the same manner as theimage-forming method described in Japanese Patent ProvisionalPublication No. 61(1986)-69062 (corresponding to U.S. Pat. No. 4,629,676and European Patent Provisional Publication No. 0174634A2), a base canbe added to the light-sensitive layer simultaneously with or prior tothe development process. Various means can be employed for adding thebase to the light-sensitive layer, for example, coating a solution ofthe base on the light-sensitive layer, immersing the light-sensitivematerial in the solution of the base, or placing the material on anothersheet containing the base. Among these means, the sheet containing thebase is preferably employed. The light-sensitive material is preferablywetted by water prior to pressing it on the sheet containing the base tosmoothly transfer the base from the sheet to the light-sensitive layer.

The construction of the light-sensitive material in which the pH valueof the light-sensitive layer rises by itself in the development processis described below.

The light-sensitive material can be so constructed that the base isisolated from the components of the light-sensitive layer in thepreservation and the base comes in contact with the components in thedevelopment process. Alternatively, the light-sensitive material can beso constructed that the light-sensitive layer can contain the base andan acid having such property that it can be vaporized or decomposed inthe development process. In the latter construction, the base and theacid can form a salt which functions as a base precursor.

An example of the former construction is a light-sensitive material inwhich a base or base precursor contained in microcapsules. The shell ofthe microcapsule containing the base or base precursor is preferablycomposed of a thermal plastic material having a melting point orsoftening point in the range of 50° to 200° C., in the case that a heatdevelopment is utilized for developing the light-sensitive material. Thebase or base precursor can be contained in the microcapsules undercondition that the base or base precursor is dissolved or dispersed inan aqueous solution of a water retention agent, or under condition thatthe base or base precursor is adsorbed on solid particles.

Another example of the former construction is a light-sensitive materialin which a base or base precursor is contained in a different layer fromthe light-sensitive layer. Further, a barrier layer is preferablyprovided between the light-sensitive layer and the layer containing abase or base precursor, said barrier layer keeping the base or baseprecursor from the light-sensitive layer and, when heated, allowingtransmission of the base or base precursor therethrough.

The base and base precursor, which can be used for raising the pH valueof the light-sensitive layer in the development process, are describedbelow.

Preferred examples of the inorganic bases include hydroxides of alkalimetals or alkaline earth metals; secondary or tertiary phosphates,borates, carbonates, quinolinates and metaborates of alkali metals oralkaline earth metals; a combination of zinc hydroxide or zinc oxide anda chelating agent (e.g., sodium picolinate); ammonium hydroxide;hydroxides of quaternary alkylammoniums; and hydroxides of other metals.Preferred examples of the organic bases include aliphatic amines (e.g.,trialkylamines, hydroxylamines and aliphatic polyamines); aromaticamines (e.g., N-alkyl-substituted aromatic amines,N-hydroxylaklyl-substituted aromatic amines andbis[p-(dialkylamino)phenyl]-methanes), heterocyclic amines, amidines,cyclic amidines, guanidines, and cyclic guanidines. Of these bases,those having a pKa of 7 or more are preferred.

In the light-sensitive material containing a base precursor, the pHvalue of the light-sensitive layer can rise by itself in the developmentprocess without keeping the base precursor from the components of thelight-sensitive layer. The base precursors preferably are those capableof releasing bases upon reaction by heating, such as salts between basesand organic acids capable of decarboxylation by heating, compoundscapable of releasing amines through intramolecular nucleophilicsubstitution, Lossen rearrangement, or Beckmann rearrangement, and thelike; and those capable of releasing bases by electrolysis. Preferredexamples of the base precursors include guanidine trichloroacetate,piperidine trichloroacetate, morpholine trichloroacetate, p-toluidinetrichloroacetate, 2-picoline trichloroacetate, guanidinephenylsulfonylacetate, guanidine 4-chlorophenylsulfonylacetate,guanidine 4-methyl-sulfonylphenylsulfonylacetate, and4-acetylaminomethyl propionate.

In the case that the components of the light-sensitive layer arecontained in microcapsules, the base precursor is preferably arrangedoutside of the microcapsules.

These bases or base precursors are preferably used in an amount of notmore than 50% by weight, and more preferably from 0.1 to 40% by weight,based on the total solid content of the light-sensitive layer. Thesebases or base precursors can be used singly or in combination.

The silver halide, the reducing agent, the polymerizable compound andthe support which constitute the light-sensitive material of theinvention are described below. Thus composed material is referredhereinafter to as "light-sensitive material".

There is no specific limitation with respect to silver halide containedin the light-sensitive layer of the light-sensitive material. Examplesof the silver halides include silver chloride, silver bromide, silveriodide, silver chlorobromide, silver chloroiodide, silver iodobromide,and silver chloroiodobromide in the form of grains.

The halogen composition of individual grains may be homogeneous orheterogeneous. The heterogeneous grains having a multilayered structurein which the halogen composition varies from the core to the outer shell(see Japanese Patent Provisional Publication Nos. 57(1982)-154232,58(1983)-108533, 59(1984)-48755 and 59(1984)-52237, U.S. Pat. No.4,433,048, and European Patent No. 100,984) can be employed. A silverhalide grain having a core/shell structure in which the silver iodidecontent in the shell is higher than that in the core can be alsoemployed.

There is no specific limitation on the crystal habit of silver halidegrains. For example, a tubular grain having an aspect ratio of not lessthan 3 can be used.

Two or more kinds of silver halide grains which differ in halogencomposition, crystal habit, grain size, and/or other features from eachother can be used in combination.

There is no specific limitation on grain size distribution of silverhalide grains. For example, the silver halide grains having such a grainsize distribution that the coefficient of the variation is not more than20% can be employed.

The silver halide grains ordinarily have a mean size of 0.001 to 5 μm,more preferably 0.001 to 2 μm.

The total silver content (including silver halide and an organic silversalt which is one of optional components) in the light-sensitive layerpreferably is in the range of from 0.1 mg/m² to 10 g/m². The silvercontent of the silver halide in the light-sensitive layer preferably isnot more than 0.1 g/m², more preferably in the range of from 1 mg to 90mg/m².

The reducing agent employed in the light-sensitive material has afunction of reducing the silver halide and/or a function of acceleratingor restraining a polymerization of the polymerizable compound. Examplesof the reducing agents having these functions include various compounds,such as hydroquinones, catechols, p-aminophenols, p-phenylenediamines,3-pyrazolidones, 3-aminopyrazoles, 4-amino-5-pyrazolones,5-aminouracils, 4,5-dihydroxy-6-aminopyrimidines, reductones,aminoreductones, o- or p-sulfonamidophenols, o- orp-sulfonamidonaphthols, 2-sulfonamidoindanones,4-sulfonamido-5-pyrazolones, 3-sulfonamidoindoles,sulfonamidopyrazolobenzimidazoles, sulfonamidopyrazolotriazoles,α-sulfonamidoketones, hydrazines, etc. Depending on the nature or amountof the reducing agent, the polymerizable compound within either the areawhere a latent image of the silver halide has been formed or the areawhere a latent image of the silver halide has not been formed can bepolymerized. In the developing system in which the polymerizablecompound within the area where the latent image has not been formed ispolymerized, 1-phenyl-3-pyrazolidone is preferably employed as thereducing agent.

The light-sensitive materials employing the reducing agent having thesefunctions (including compounds referred to as developing agent,hydrazine derivative or precursor of reducing agent) are described inJapanese Patent Provisional Publication Nos. 61(1986)-183640,61(1986)-188535 and 61(1986)-228441. These reducing agents are alsodescribed in T. James, "The Theory of the Photographic Process", 4thedition, 291-334 (1977), Research Disclosure No. 17029, 9-15 (June1978), and Research Disclosure No. 17643, 22-31 (December 1978). Thereducing agents described in the these publications can be employed inthe light-sensitive material of the present invention. Thus, "thereducing agent(s)" in the present specification means to include all ofthe reducing agents described in the above mentioned publications.

These reducing agents can be used singly or in combination. In the casethat two or more reducing agents are used in combination, certaininteractions between these reducing agents may be expected. One of theinteractions is for acceleration of reduction of silver halide (and/oran organic silver salt) through so-called super-additivity. Otherinteraction is for a chain reaction in which an oxidized state of onereducing agent formed by a reduction of silver halide (and/or an organicsilver salt) induces or inhibits the polymerization of the polymerizablecompound via oxidation-reduction reaction with other reducing agent.Both interactions may occur simultaneously. Thus, it is difficult todetermine which of the interactions has occurred in practical use.

Examples of these reducing agents include pentadecylhydroquinone,5-t-butylcatechol, p-(N,N-diethylamino)phenol,1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone,1-phenyl-4-methyl-4-heptadecylcarbonyloxymethyl-3-pyrazolidone,2-phenylsulfonylamino-4-hexadecyloxy-5-t-octylphenol,2-phenylsulfonylamino-4-t-butyl-5-hexadecyloxyphenol,2-(N-butylcarbamoyl)-4-phenylsulfonylaminonaphtol,2-(N-methyl-N-octadecylcarbamoyl)-4-sulfonylaminonaphthol,1-acetyl-2-phenylhydrazine, 1-acetyl-2-(p- or o-aminophenyl)hydrazine,1-formyl-2-(p- or o-aminophenyl)hydrazine, 1-acetyl-2-)p- oro-methoxyphenyl)hydrazine, 1-lauroyl-2-(p- or o-aminophenyl)hydrazine,1-trityl-2-(2,6-dichloro-4-cyanophenyl)hydrazine,1-trityl-2-phenylhydrazine, 1-phenyl-2-(2,4,6-trichlorophenyl)hydrazine,1-{2-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p- oro-aminophenyl)hydrazine, 1-{2-(2,5-di-t-pentylphenoxy)butyloyl}-2-(p- oro-aminophenyl)hydrazine pentadecylfluorocaprylate salt, 3-indazolinone,1-(3,5-dichlorobenzoyl)-2-phenylhydrazine,1-trityl-2-[{(2-N-butyl-N-octylsulfamoyl)-4-methanesulfonyl}phenyl]hydrazine,1-{4-(2,5-di-tert-pentylphenoxy)butyloyl}-2-(p-oro-methoxyphenyl)hydrazine,1-(methoxycarbonylbenzohydryl)-2-phenylhydrazine,1-formyl-2-[4-{2-(2,4-di-tert-pentyl-phenoxy)butylamide}phenyl]hydrazine,1-acetyl-2-[4-{2-(2,4-di-tert-pentylphenoxy)butylamido}phenyl]hydrazine,1-trityl-2-[{2,6-dichloro-4-(N,N-di-2-ethylhexyl)carbamoyl}phenyl]hydrazine,1-(methoxycarbnylbenzohydryl)-2-(2,4-dichlorophenyl)hydrazine,1-trityl-2-[{2-(N-ethyl-N-octylsulfamoyl)-4-methansulfonyl}phenyl]hydrazine,1-benzoyl-2-tritylhydrazine, 1-(4-butoxybenzoyl)-2-tritylhydrazine,1-(2,4-dimethoxybenzoyl)-2-tritylhydrazine,1-(4-dibutylcarbamoylbenzoyl)-2-trityhydrazine and1-(1-naphthoyl)-2-tritylhydrazine.

Among these reducing agents, a compound having a pKa value of not lowerthan 9 is preferred, wherein the value is measured under a conditionthat the solvent is dimethylformamide (DMF).

The present inventor has found that the reducing agent having a pKavalue of not lower than 9 is remarkably stable in the light-sensitivematerial of the invention. Therefore, the light-sensitive materialcontaining the reducing agent having a pKa value of not lower than 9 ismore improved in the preservability.

The pKa value of the reducing agent more preferably is not lower than10. Further, in view of the function of the reducing agent, the pKavalue preferably is not higher than 16.

The amount of the reducing agent in the light-sensitive layer preferablyranges from 0.1 to 1,500 mole % based on the amount of silver (containedin the abovementioned silver halide and an organic silver salt).

There is no specific limitation with respect to the polymerizablecompound, and any known polymerizable compounds including monomers,oligomers and polymers can be contained in the light-sensitive layer. Inthe case that heat development (i.e., thermal development) is utilizedfor developing the light-sensitive material, the polymerizable compoundshaving a relatively higher boiling point (e.g., 80° C. or higher) thatare hardly evaporated upon heating are preferably employed. In the casethat the light-sensitive layer contains a color image forming substance,the polymerizable compounds are preferably cross-linkable compoundshaving plural polymerizable groups in the molecule, because suchcross-linkable compounds favorably serve for fixing the color imageforming substance in the course of polymerization hardening of thepolymerizable compounds.

The polymerizable compound employable for the light-sensitive materialare described in the above-mentioned and later-mentioned publicationsconcerning the light-sensitive material.

Preferred polymerizable compounds employable for the light-sensitivematerial are compounds which are polymerizable through addition reactionor ring-opening reaction. Preferred examples of the compounds beingpolymerizable through addition reaction include compounds having anethylenic unsaturated group. Preferred examples of the compounds beingpolymerizable through ringopening reaction include the compounds havingan epoxy group. Among them, the compounds having an ethylenicunsaturated group are preferred.

Examples of compounds having an ethylenic unsaturated group includeacrylic acid, salts of acrylic acid, acrylic esters, acrylamides,methacrylic acid, salts of methacrylic acid, methacrylic esters,methacrylamide, maleic anhydride, maleic esters, itaconic esters,styrene, styrene derivatives, vinyl ethers, vinyl esters, N-vinylheterocyclic compounds, allyl ethers, allyl esters, and compoundscarrying a group of groups corresponding to one or more of thesecompunds.

Concrete examples of the acrylic esters include nbutyl acrylate,cyclohexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, furfurylacrylate, ethoxyethoxy acrylate, dicyclohexyloxyethyl acrylate,nonylphenyloxyethyl acrylate, hexanediol diacrylate, butanedioldiacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate,pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,diacrylate of polyoxyethylenated bisphenol A, polyacrylate ofhydroxypolyether, polyester acrylate, and polyurethane acrylate.

Concrete examples of the methacrylic esters include methyl methacrylate,butyl methacrylate, ethylene glycol dimethacrylate, butanedioldimethacrylate, neopentylglycol dimethacrylate, trimethylolpropanetrimethacrylate, pentaerythriotol trimethacrylate, pentaerythritoltetramethacrylate, and dimethacrylate of polyoxyalkylenated bisphenol A.

The polymerizable compounds can be used singly or in combination of twoor more compounds. For example, a mixture of two or more polymerizablecompounds can be employed. Further, compounds formed by bonding apolymerizable group such as a vinyl group or a vinylidene group to areducing agent or a color image forming substance are also employed asthe polymerizable compounds. The light-sensitive materials employingthese compounds which show functions as both the reducing agent and thepolymerizable compounds, or of the color image forming substance and thepolymerizable compound are included in embodiments of the invention.

The amount of the polymerizable compound for incorporation into thelight-sensitive layer preferably ranges from 5 to 1.2×10⁵ times (byweight) as much as the amount of silver halide, more preferably from 10to 1×10⁴ times as much as the silver halide.

The light-sensitive material can be prepared by arranging alight-sensitive layer containing the abovementioned components on asupport. There is no limitation with respect to the support. In the casethat heat development is utilized in the use of the light-sensitivematerial, the material of the support preferably is resistant to heatgiven in the processing stage. Examples of the material employable forthe preparation of the support include glass, paper, fine paper, coatpaper, synthetic paper, metals and analogues thereof, polyester, acetylcellulose, cellulose ester, polyvinyl acetal, polystyrene,polycarbonate, polyethylene terephthalate, and paper laminated withresin or polymer (e.g., polyethylene). In the case that a porousmaterial, such as paper is employed as the support, the porous supportpreferably has such a surface characteristic that a filtered maximumwaviness of not less than 4 μm is observed in not more than 20 positionsamong 100 positions which are determined at random on a filteredwaviness curve obtained according to JIS-B-0610.

Various embodiments of the light-sensitive materials, optionalcomponents which may be contained in the light-sensitive layer, andauxiliary layers which may be optionally arranged on the light-sensitivematerials are described below.

The polymerizable compound is preferably dispersed in the form of oildroplets in the light-sensitive layer. Other components in thelight-sensitive layer, such as silver halide, the reducing agent, thecolor image forming substances may be also contained in the oildroplets.

The oil droplets of the polymerizable compound are preferably preparedin the form of microcapsules. There is no specific limitation onpreparation of the microcapsules.

There is also no specific limitation on shell material of themicrocapsule, and various known materials such as polymers which areemployed in the conventional microcapsules can be employed as the shellmaterial. Examples of the shell material include polyamide resin and/orpolyester resin, polyurea resin and/or polyurethane resin, aminoaldehideresin, gelatin, epoxy resin, a complex resin containing polyamide resinand polyurea resin, a complex resin containing polyurethane resin andpolyester resin.

The mean size of the microcapsule preferably ranges from 0.5 to 50 μm,more preferably 1 to 25 μm, most preferably 3 to 20 μm. In the case thatsilver halide grains are contained in the microcapsule, the mean grainsized of the silver halide grains preferably is not more than the 5thpart of the mean size of the microcapsules, more preferably is not morethan the 10th part. It is observed that when the mean sized of themicrocapsules is not less than 5 times as much as the mean grain size ofsilver halide grains, even and uniform image can be obtained.

In the case that silver halide grains are contained in the microcapsule,the silver halide grains are preferably arranged in the shell materialof the microcapsules.

Further, two or more kinds of the microcapsules differing from eachother with respect to at least one of the silver halide, thepolymerizable compound and the color image forming substance can beemployed. Furthermore, three or more kinds of the microcapsules,differing from each other with respect to the color image formingsubstance is preferably employed to form a full color image.

The light-sensitive layer can further contain optional components suchas color image forming substances, sensitizing dyes, organic silversalts, various kinds of image formation accelerators, thermalpolymerization inhibitors, thermal polymerization initiators,development stopping agents, fluorescent brightening agents,discoloration inhibitors, antihalation dyes or pigments, antiirradiationdyes or pigments, matting agents, antismudging agents, plasticizers,water releasers, binders, photo polymerization initiator and solvent ofthe polymerizable compound.

There is no specific limitation with respect to the color image formingsubstance, and various kinds of substances can be employed. Thus,examples of the color image forming substance include both coloredsubstance (i.e., dyes and pigments) and non-colored or almostnon-colored substance (i.e., color former or dye- or pigmentprecursor)which develops to give a color under application of external energy(e.g., heating, pressing, light irradiation, etc.) or by contact withother components (i.e., developer). The light-sensitive material usingthe color image forming substance is described in Japanese PatentProvisional Publication No. 61(1986)-73145 (corresponding to U.S. Pat.No. 4,629,676 and European Patent Provisional Publication No.0174634A2).

Examples of the dyes and pigments (i.e., colored substances) employablein the invention include commercially available ones, as well as variousknown compounds described in the technical publications, e.g., YukiGosei Kagaku Kyokai (ed.), Handbook of Dyes (in Japanese, 1970) andNippon Ganryo Gijutsu Kyokai (ed.), New Handbook of Pigments (inJapanese, 1977). These dyes and pigments can be used in the form of asolution or a dispersion.

Examples of the substances which develop to give a color by certainenergy includes thermochromic compounds, piezochromic compounds,photochromic compounds and leuco compounds derived from triarylmethanedyes, quinone dyes, indigoid dyes, azine dyes, etc. These compounds arecapable of developing a color by heating, application of pressure,light-irradiation or air-oxidation.

Examples of the substances which develop to give a color in contact withother components include various compounds capable of developing a colorthrough some reaction between two or more components, such as acidbasereaction, oxidation-reduction reaction, coupling reaction, chelatingreaction, and the like. Examples of such color formation systems aredescribed in Hiroyuki Moriga, "Introduction of Chemistry of SpecialityPaper" (in Japanese, 1975), 29-58 (pressure-sensitive copying paper),87-95 (azo-graphy), 118-120 (heat-sensitive color formation by achemical change) or in MSS. of the seminer promoted by the Society ofKinki Chemical Industry, "The Newest Chemistry of Coloring Matter -Attractive Application and New Development as a Functional ColoringMatter", 26-32 (June, 19, 1980). Examples of the color formation systemsspecifically include a color formation system used in pressure-sensitivepapers, etc., comprising a color former having a partial structure oflactone, lactam, spiropyran, etc., and an acidic substance (developer),e.g., acid clay, phenol, etc.; a system utilizing azo-coupling reactionbetween an aromatic a diazonium salt, diazotate or diazosulfonate andnaphthol, aniline, active methylene, etc.; and system utilizing achelating reaction, such as a reaction between hexamethylenetetramineand a ferric ion and gallic acid, or a reaction between aphenolphthalein-complexon and an alkaline earth metal ion; a systemutilizing oxidation-reduction reaction, such as a reaction betweenferric stearate and pyrogallol, or a reaction between silver behenateand 4-methoxy-1-naphtol, etc.

In the case that the color image forming substance comprising twocomponents (e.g., a color former and a developer), one component and thepolymerizable compound is contained in the microcapsule, and the othercomponent is arranged outside of the microcapsule in the light-sensitivelayer, a color image can be formed on the light-sensitive layer.

The color image forming substance in the light-sensitive material ispreferably used in an amount of from 0.5 to 50 parts by weight, and morepreferably from 2 to 30 parts by weight, per 100 parts by weight of thepolymerizable compound. In the case that the developer is used, it ispreferably used in an amount of from about 0.3 to about 80 parts byweight per one part by weight of the color former.

There is no specific limitation with respect to the sensitizing dyes,and known sensitizing dyes used in the conventional art of photographymay be employed in the light-sensitive material. Examples of thesensitizing dyes include methine dyes, cyanine dyes, merocyanine dyes,complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes,hemicyanine dyes, styryl dyes, and hemioxonol dyes. These sensitizingdyes can be used singly or in combination. Combinations of sensitizingdyes are often used for the purpose of supersensitization. In additionto the sensitizing dyes, a substance which does not per se exhibitspectral sensitization effect or does not substantially absorb visiblelight but shows supersensitizing activity can be used. The amount of thesensitizing dye to be added generally ranges from about 10.sup.×8 toabout 10.sup.×2 mol per 1 mol of silver halide. The sensitizing dye ispreferably added during the stage of the preparation of the silverhalide emulsion (simultaneously with or after the grain formation).

When the heat development is employed in the use of the light-sensitivematerial, an organic silver salt is preferably contained in thelight-sensitive material. It can be assumed that the organic silver salttakes part in a redox reaction using a silver halide latent image as acatalyst when heated to a temperature of 80° C. or higher. In such case,the silver halide and the organic silver salt preferably are located incontact with each other or close together. Examples of organic compoundsemployable for forming such organic silver salt include aliphatic oraromatic carboxylic acids, thiocarbonyl group-containing compoundshaving a mercapto group or an α-hydrogen atom, imino group-containingcompounds, and the like. Among them, benzotriazoles are most preferable.The organic silver salt is preferably used in an amount of from 0.01 to10 mol., and preferably from 0.01 to 1 mol., per 1 mol. of thelight-sensitive silver halide. Instead of the organic silver salt, anorganic compound (e.g., benzotriazole) which can form an organic silversalt in combination with an inorganic silver salt can be added to thelight-sensitive layer to obtain the same effect.

Various image formation accelerators are employable in thelight-sensitive material. The image formation accelerators have afunction to accelerate the oxidation-reduction reaction between a silverhalide (and/or an organic silver salt) and a reducing agent, a functionto accelerate emigration of an image forming substance from alight-sensitive layer to an image-receiving material or animage-receiving layer, or a similar function. The image formationaccelerators can be classified into oils, surface active agents,compounds functioning as an antifogging agent and/or a developmentaccelerator, hotmelt solvents, antioxidants and the like. These groups,however, generally have certain combined functions, i.e., two or more ofthe above-mentioned effects. Thus, the above classification is for thesake of convenience, and one compound often has a plurality of functionscombined.

Various examples of these image formation accelerators are shown below.

Examples of the oils employable in the invention include high-boilingorganic solvents which are used as solvents in emulsifying anddispersing hydrophobic compounds.

Examples of the surface active agents employable in the inventioninclude pyridinium salts, ammonium salts and phosphonium salts asdescribed in Japanese Patent Provisional Publication No. 59(1984)-74547;polyalkylene oxides as described in Japanese Patent ProvisionalPublication No. 59(1984)-57231.

The compounds functioning as an antifogging agent and/or a developmentaccelerator are used to give a clear image having a high maximum densityand a low minimum density (an image having high contrast). Examples ofthe compounds include a 5- or 6-membered nitrogen containingheterocyclic compound (e.g., a cyclic amide compound), a thioureaderivative, a thioether compound, a polyethylene glycol derivative, athiol derivative, an acetylene compound and a sulfonamide derivative.

The hot-melt solvents preferably are compounds which may be used assolvent of the reducing agent or those which have high dielectricconstant and can accelerate physical development of silver salts.Examples of the hot-melt solvents include polyethylene glycols,derivatives of polyethylene oxides (e.g., oleate ester), beeswax,monstearin and high dielectric constant compounds having --SO₂ --and/or--CO--group described in U.S. Pat. No. 3,347,675; polar compoundsdescribed in U.S. Pat. No. 3,667,959; and 1,10-decanediol, methylanistate and biphenyl suberate described in Research Disclosure 26-28(December 1976). The light-sensitive material employing the hot-meltsolvents is described in Japanese Patent Application No.60(1985)-227527. The hot-melt solvent is preferably used in an amount offrom 0.5 to 50% by weight, and more preferably from 1 to 20% by weight,based on the total solid content of the light-sensitive layer.

The antioxidants can be used to eliminate the influence of the oxygenwhich has an effect of inhibiting polymerization in the developmentprocess. Example of the antioxidants is a compound having two or moremercapto groups.

The thermal polymerization initiators employable in the light-sensitivematerial preferably are compounds that are decomposed under heating togenerate a polymerization initiating species, particularly a radical,and those commonly employed as initiators of radical polymerization. Thethermal polymerization initiators are described in "AdditionPolymerization and Ring Opening Polymerization", 6-18, edited by theEditorial Committee of High Polymer Experimental Study of the HighPolymer Institute, published by Kyoritsu Shuppan (1983). Examples of thethermal polymerization initiators include azo compounds, e.g.,azobisisobutyronitrile, 1,1'-azobis(1-cyclohexanecarbonitrile), dimethyl2,2'-azobisisobutyrate, 2,2'-azobis(2-methylbutyronitrile), andazobisdimethylvaleronitrile; organic peroxides, e.g., benzoyl peroxides,di-tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, andcumene hydroperoxide; inorganic peroxides, e.g., hydrogen peroxide,potassium persulfate, and ammoniuim persulfate; and sodiump-toluenesulfinate. The thermal polymerization initiators are preferablyused in an amount of from 0.1 to 120% by weight, and more preferablyfrom 1 to 10% by weight, based on amount of the polymerizable compound.In a system in which the polymerizable compound within the area wherethe latent image has not been formed is polymerized, the thermalpolymerization initiators are preferably incorporated into thelight-sensitive layer. The light-sensitive material employing thethermal polymerization initiators is described in Japanese PatentProvisional Publication No. 61(1986)-260241.

The development stopping agents employable in the light-sensitivematerial are compounds that neutralize a base or react with a base toreduce the base concentration in the layer to thereby stop development,or compounds that mutually react with silver or a silver salt tosuppress development. More specifically, examples of the developmentstopping agents include acid precursors capable of releasing acids uponheating electrophilic compounds capable of undergoing substitutionreaction with a coexisting base upon heating, nitrogen-containingheterocyclic compounds, mercapto compounds, and the like. Examples ofthe acid precursors include oxide esters described in Japanese PatentProvisional Publication Nos. 60(1985)-108837 and 60(1985)-192939 andcompounds which release acids through Lossen rearrangement described inJapanese Patent Provisional Publication No. 60(1985)-230133. Examples ofthe electrophilic compounds which induce substitution reaction withbases upon heating are described in Japanese Patent ProvisionalPublication No. 60(1985)-230134.

The antismudging agents employable in the light-sensitive materialpreferably are particles which are solid at ambient temperatures.Examples of the antismudging agents include starch particles describedin U.K. Patent No. 1,232,347; polymer particles described in U.S. Pat.No. 3,625,736; microcapsule particles containing no color formerdescribed in U.K. Patent No. 1,235,991; and cellulose particles, andinorganic particles, such as particles of talc, kaolin, bentonite,agalmatolite, zinc oxide, titanium dioxide or aluminum oxide describedin U.S. Pat. No. 2,711,375. Such particles preferably have a mean sizeof 3 to 50 μm, more preferably 5 to 40 μm. When the microcapsule isemployed in the light-sensitive material, the size of said particle ispreferably larger than that of the microcapsule.

Binders employable in the light-sensitive material preferably aretransparent or semi-transparent hydrophilic binders. Examples of thebinders include natural substances, such as gelatin, gelatinderivatives, cellulose derivatives, starch, and gum arabic; andsynthetic polymeric substances, such as water-soluble polyvinylcompounds e.g., polyvinyl alcohol, polyvinylpyrrolidone, and acrylamidepolymers. In addition to the synthetic polymeric substances, vinylcompounds dispersed in the form of latex, which are particularlyeffective to increase dimensional stability of photographic materials,can be also used. These binders can be used singly or in combination.The light-sensitive material employing a binder is described in JapanesePatent Provisional Publication No. 61(1986)-69062 (corresponding to U.S.Pat. No. 4,629,676 and European Patent Provisional Publication No.0174634A2).

The photo polymerization initiator can be contained in thelight-sensitive layer to polymerize the unpolymerized polymerizablecompound after the image-formation.

In the case that the solvent of the polymerizable compound is used, thesolvent is preferably contained in a microcapsule which is differentfrom the microcapsule contained the polymerizable compound.

Examples and usage of the other optional components which can becontained in the light-sensitive layer are also described in theabove-mentioned publications and applications concerning thelight-sensitive material, and in Research Disclosure Vol. 170, No.17029, 9-15 (June 1978).

Examples of auxiliary layers which are optionally arranged on thelight-sensitive material include an image-receiving layer, a heatinglayer, an antistatic layer, an anticurl layer, a release layer, a coversheet or a protective layer, a layer containing a base or base precursorand a base barrier layer.

Instead of the use of the image-receiving material, the image-receivinglayer can be arranged on the light-sensitive material to produce thedesired image on the image-receiving layer of the light-sensitivematerial. The image-receiving layer of the light-sensitive material canbe constructed in the same manner as the layer of the image-receivingmaterial.

The light-sensitive material can be prepared, for instance, by thefollowing process.

The light-sensitive material is usually prepared by dissolving,emulsifying or dispersing each of the components of the light-sensitivelayer in an adequate medium to obtain coating solution, and then coatingthe obtained coating solution on a support.

The coating solution can be prepared by mixing liquid compositions eachcontaining a component of the light-sensitive layer. Liquid compositioncontaining two or more components may be also used in the preparation ofthe coating solution. Some components of the light-sensitive layer canbe directly added to the coating solution or the liquid composition.Further, a secondary composition can be prepared by emulsifying the oily(or aqueous) composition in an aqueous (or oily) medium to obtain thecoating solution.

The silver halide is preferably prepared in the form of a silver halideemulsion. Various processes for the preparation of the silver halideemulsion are known in the conventional technology for the preparation ofphotographic materials.

The silver halide emulsion can be prepared by the acid process, neutralprocess or ammonia process. In the stage for the preparation, a solublesilver salt and a halogen salt can be reacted in accordance with thesingle jet process, double jet process or a combination thereof. Areverse mixing method, in which grains are formed in the presence ofexcess silver ions, or a controlled double jet process, in which a pAgvalue is maintained constant, can be also employed. In order toaccelerate grain growth, the concentrations or amounts or the silversalt and halogen salt to be added or the rate of their addition can beincreased as described in Japanese Patent Provisional Publication Nos.55(1980)-142329 and 55(1980)-158124, and U.S. Pat. No. 3,650,757, etc.

The silver halide emulsion may be of a surface latent image type thatforms a latent image predominantly on the surface of silver halidegrains, or of an inner latent image type that forms a latent imagepredominantly in the interior of the grains. A direct reversal emulsioncomprising an inner latent image type emulsion and a nucleating agentmay be employed. The inner latent image type emulsion suitable for thispurpose is described in U.S. Pat. Nos. 2,592,250 and 3,761,276, JapanesePatent Publication No. 58(1983)-3534 and Japanese Patent ProvisionPublication No. 57(1982)-136641, etc. The nucleating agent that ispreferably used in combination with the inner latent image type emulsionis described in U.S. Pat. Nos. 3,227,552, 4,245,037, 4,255,511,4,266,013 and 4,276,364, and West German Patent Provisional Publication(OLS) No. 2,635,316.

In the preparation of the silver halide emulsions, hydrophilic colloidsare advantageously used as protective colloids. Examples of usablehydrophilic colloids include proteins, e.g., gelatin, gelatinderivatives, gelatin grafted with other polymers, albumin, and casein;cellulose derivatives, e.g., hydroxyethyl cellulose, carboxymethylcellulose, cellulose sulfate, etc.; saccharide derivatives, e.g., sodiumalginate and starch derivatives; and a wide variety of synthetichydrophilic polymers, such as polyvinyl alcohol, polyvinyl alcoholpartial acetal, poly-N-vinylpyrrolidone, polyacrylic acid,polymethacrylic acid, polyacrylamide, polyvinylimidazole, andpolyvinylpyrazole, and copolymers comprising monomers constituting thesehomopolymers. Among them, gelatin is most preferred, Examples ofemployable gelatins include not only lime-processed gelatin, but alsoacid-processed gelatin and enzyme-processed gelatin. Hydrolysis productsor enzymatic decomposition products of gelatin can also be used.

In the formation of silver halide grains in the silver halide emulsion,ammonia, an organic thioether derivative as described in Japanese PatentPublication No. 47(1972)-11386 or sulfur-containing compound asdescribed in Japanese Patent Provisional Publication No. 53(1978) 144319can be used as a silver halide solvent. Further, in the grain formationor physical ripening, a cadmium salt, a zinc salt, a lead salt, athallium salt, or the like can be introduced into the reaction system.Furthermore, for the purpose of overcoming high or low intensityreciprocity law failure, a water-soluble iridium salt, e.g., iridium(III) or (IV) chloride, or ammonium hexachloroiridate, or awater-soluble rhodium salt, e.g., rhodium chloride can be used.

After the grain formation or physical ripening, soluble salts may beremoved from the resulting emulsion by a known noodle washing method ora sedimentation method. The silver halide emulsion may be used in theprimitive condition, but is usually subjected to chemical sensitization.Chemical sensitization can be carried out by the sulfur sensitization,reduction sensitization or noble metal sensitization, or a combinationthereof that are known for emulsions for the preparation of theconventional light-sensitive materials.

When the sensitizing dyes are added to the silver halide emulsion, thesensitizing dye is preferably added during the preparation of theemulsion. When the organic silver salts are introduced in thelight-sensitive microcapsule, the emulsion of the organic silver saltscan be prepared in the same manner as in the preparation of the silverhalide emulsion.

In preparation of the light-sensitive material, the polymerizablecompounds are used as the medium for preparation of the liquidcomposition containing another component of the light-sensitive layer.For example, the silver halide, including the silver halide emulsion),the reducing agent, or the color image forming substance can bedissolved, emulsified or dispersed in the polymerizable compound toprepare the light-sensitive material. Especially, the color imageforming substance is preferably incorporated in the polymerizablecompound. Further, the necessary components for preparation of amicrocapsule, such as shell material can be incorporated into thepolymerizable compound.

The light-sensitive composition which is the polymerizable compoundcontaining the silver halide can be prepared using the silver halideemulsion. The light-sensitive composition can be also prepared usingsilver halide powders which can be prepared by lyophilization. Theselight-sensitive composition can be obtained by stirring thepolymerizable compound and the silver halide using a homogenizer, ablender, a mixer or other conventional stirring device.

Polymers having a principal chain consisting essentially of ahydrocarbon chain substituted in part with hydrophilic groups whichcontain, in their terminal groups, --OH or nitrogen having a loneelectron-pair are preferably introduced into the polymerizable compoundprior to the preparation of the light-sensitive composition. The polymerhas a function of dispersing silver halide or other component in thepolymerizable compound very uniformly as well as a function of keepingthus dispered state. Further, the polymer has another function ofgathering silver halide along the interface between the polymerizablecompound (i.e., light-sensitive composition) and the aqueous medium inpreparation of the microcapsule. Therefore, using this polymer, silverhalide can be easily introduced into the shell material of themicrocapsule.

The polymerizable compound (including the light-sensitive composition)are preferably emulsified in an aqueous medium to prepare the coatingsolution. The necessary components for preparation of the microcapsule,such as shell material can be incorporated into the emulsion. Further,other components such as the reducing agent can be added to theemulsion.

The emulsion of the polymerizable compound can be processed for formingshell of the microcapsule. Examples of the process for the preparationof the microcapsules include a process utilizing coacervation ofhydrophilic wall-forming materials as described in U.S. Pat. Nos.2,800,457 and 2,800,458; an interfacial polymerization process asdescribed in U.S. Patent No. 3,287,154, U.K. Patent No. 990,443 andJapanese Patent Publication Nos. 38(1963)-19574, 42(1967)-446 and42(1967)-771; a process utilizing precipitation of polymers as describedin U.S. Pat. Nos. 3,418,250 and 3,660,304; a process of usingisocyanate-polyol wall materials as described in U.S. Pat. No.3,796,669; a process of using isocyanate wall materials as described inU.S. Pat. No. 3,914,511; a process of using ureaformaldehyde orurea-formaldehyde-resorcinol wall-forming materials as described in U.S.Pat. Nos. 4,001,140, 4,087,376 and 4,089,802; a process of usingmelamineformaldehyde resins hydroxypropyl cellulose or like wall-formingmaterials as described in U.S. Pat. No. 4,025,455; an in situ processutilizing polymerization of monomers as described in U.K. Patent No.867,797 and U.S. Pat. No. 4,001,140; an electrolytic dispersion andcooling process as described in U.K. Patent Nos. 952,807 and 965,074; aspray-drying process as described in U.S. Pat. No. 3,111,407 and U.K.Patent 930,422; and the like. It is preferable, though not limitative,that the microcapsule is prepared by emulsifying core materialscontaining the polymerizable compound and forming a polymeric membrane(i.e., shell) over the core materials.

When the emulsion of the polymerizable compound (including thedispersion of the microcapsule) has been prepared by using thelight-sensitive composition, the emulsion can be used as the coatingsolution of the light-sensitive material. The coating solution can bealso prepared by mixing the emulsion of the polymerizable compound andthe silver halide emulsion. The other components can be added to thecoating solution in a similar manner as the emulsion of thepolymerizable compound.

The coating solution of the light-sensitive layer can be adjusted withan acid to form the layer having a pH value of not higher than 7. The pHvalue of the light-sensitive layer can be easily adjusted in the stageof the coating solution, because a strong correlation between the pHvalues of the coating solution and the light-sensitive layer isgenerally valid even if there is a difference between these pH values.

A light-sensitive material of the invention can be prepared by coatingand drying the above-prepared coating solutions on a support in theconventional manner.

Use of the light-sensitive material is described below.

In the use of the light-sensitive material of the invention, adevelopment process is conducted simultaneously with or after animagewise exposure.

Various exposure means can be employed in the imagewise exposure, and ingeneral, the latent image on the silver halide is obtained by imagewiseexposure to radiation including visible light. The type of light sourceand exposure can be selected depending on the light-sensitivewavelengths determined by spectral sensitization or sensitivity ofsilver halide. Original image can be either monochromatic image or colorimage.

Development of the light-sensitive material can be conductedsimultaneously with or after the imagewise exposure. The development canbe conducted using a developing solution in the same manner as the imageforming method described in Japanese Patent Publication No.45(1970)-11149 (corresponding to U.S. Pat. No. 3,697,275). The imageforming method described in Japanese Patent Provisional Publication No.61(1986)-69062 (corresponding to U.S. Pat. No. 4,629,676 and EuropeanPatent Provisional Publication No. 0174634A2) which employs a heatdevelopment process has an advantage of simple procedures and shortprocessing time because of the dry process. Thus, the latter method ispreferred as the development process of the light-sensitive material.

Heating in the heat development process can be conducted in variousknown manners. The heating layer which is arranged on thelight-sensitive material can be used as the heating means in the samemanner as the light-sensitive material described in Japanese PatentProvisional Publication No. 61(1986)-294434. Further, thelight-sensitive material can be heated while suppressing supply ofoxygen into the light-sensitive layer from outside. Heating temperaturesfor the development process usually ranges from 80° C. to 200° C., andpreferably from 100° C. to 160° C. Various heating patterns areapplicable. The heating time is usually not shorter than 1 second, andpreferably from 1 second to 5 minutes, and more preferably from 1 secondto 1 minute.

During the above development process, a polymerizable compound withinthe area where a latent image of the silver halide has been formed orwithin the area where a latent image of the silver halide has not beenformed is polymerized. In a general system, the polymerizable compoundwithin the area where the latent image has been formed is polymerized.If a nature or amount of the reducing agent is controlled, thepolymerizable compound within the area where the latent image has notbeen formed can be polymerized.

In the above development process, a polymer image can be formed on thelight-sensitive layer. A pigment image can be also obtained by fixingpigments to the polymer image.

Further, a color image can be formed on the light-sensitive material inwhich the light-sensitive layer contains a color former and a developer,one of them is together with the polymerizable compound contained in amicrocapsule, and the other is arranged outside of the microcapsule.

The image can be also formed on the image-receiving material. Theimage-receiving material is described hereinbelow. The image formingmethod employing the image-receiving material or the image-receivinglayer is described in Japanese Patent Provisional Publication No.61(1986)-278849.

Examples of the material employable as the support of theimage-receiving material include baryta paper in addition to variousexamples which can be employed as the support of the above mentionedlight-sensitive material. In the case that a porous material, such aspaper is employed as the support of the image-receiving material , theporous support preferably has such a surface characteristic that afiltered maximum waviness of not less than 4 μm is observed in not morethan 20 positions among 100 positions which are determined at random ona filtered waviness curve obtained according to JIS-B-0610. Further, atransparent material can be employed as the support of theimage-receiving material to obtain a transparent or a projected image.

The image-receiving material is usually prepared by providing theimage-receiving layer on the support. The image-receiving layer can beconstructed according to the color formation system. In the cases that apolymer image is formed on the image-receiving material and that a dyeor pigment is employed as the color image forming substance, theimage-receiving material be composed of a simple support.

For example, when a color formation system using a color former anddeveloper is employed, the developer can be contained in theimage-receiving layer. Further, the image-receiving layer can becomposed of at least one layer containing a mordant. The mordant can beselected from the compounds known in the art of the conventionalphotography according to the kind of the color image forming substance.If desired, the image-receiving layer can be composed of two or morelayers containing two or more mordants different in the mordanting powerfrom each other.

The image-receiving layer preferably contains a polymer as binder. Thebinder which may be employed in the above-mentioned light-receivinglayer is also employable in the image-receiving layer. Further, apolymer having a transmission coefficient of oxygen of not more than1.0×10.sup.×11 cm³.cm/cm².sec.cmHg can be used as the binder to protectthe color of the image formed on the image-receiving material.

The image-receiving layer can contain a granulated thermoplasticcompound to obtain a glossy image. Further, the image-receiving layercan contain a white pigment (e.g., titanium dioxide) to function as awhite reflection layer. Furthermore, a photo polymerization initiator ora thermalpolymerization initiator can be contained in theimage-receiving layer to polymerize the unpolymerized polymerizablecompound.

The image-receiving layer can be composed of two or more layersaccording to the above-mentioned functions. The thickness of theimage-receiving layer preferably ranges from 1 to 100 μm, morepreferably from 1 to 20 μm.

A protective layer can be provided on the surface of the image-receivinglayer.

After the development process, pressing the light-sensitive material onthe the image-receiving material to transfer the unpolymerizedpolymerizable compound to the image-receiving material, a polymer imagecan be obtained in the image-receiving material. The process forpressing can be carried out in various known manners.

In the case that the light-sensitive layer contains a color imageforming substance, the color image forming substance is fixed bypolymerization of the polymerizable compound. Then, pressing thelight-sensitive material on the image-receiving material to transfer thecolor image forming substance in unfixed portion, a color image can beproduced on the image-receiving material.

The light-sensitive material can be used for monochromatic or colorphotography, printing, radiography, diagnosis (e.g., CRT photography ofdiagnostic device using supersonic wave), copy (e.g., computer-graphichard copy), etc.

The present invention is further described by the following exampleswithout limiting the invention.

EXAMPLE 1

Preparation of silver halide emulsion

In 1,000 ml of water were dissolved 20 g of gelatin and 3 g of sodiumchloride, and the resulting gelatin solution was kept at 75° C. To thegelatin solution, 600 ml of an aqueous solution containing 21 g ofsodium chloride and 56 g of potassium bromide and 600 ml of an aqueoussolution containing 0.59 mole of silver nitrate were addedsimultaneously at the same feed rate over a period of 40 minutes toobtain a silver chlorobromide emulsion having cubic grains, uniformgrain size distribution, a mean grain size of 0.35 μm and a bromidecontent of 80 mole %.

The emulsion was washed for desalting and then subjected to chemicalsensitization with 5 mg of sodium thiosulfate and 20 mg of4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene at 60° C. The yield of theemulsion was 600 g.

Preparation of silver benzotriazole emulsion

In 3,000 ml of water were dissolved 28 g of gelatin and 13.2 g ofbenzotriazole, and the solution was kept at 40° C. while stirring. Tothe solution was added 100 ml of an aqueous solution of 17 g of silvernitrate over 2 minutes. Excessive salts were sedimented and removed fromthe resulting emulsion by pH-adjustment. Thereafter, the emulsion wasadjusted to pH 6.30 to obtain a silver benzotriazole emulsion. The yieldof the emulsion was 400 g.

Preparation of light-sensitive composition

In 100 g of trimethylolpropane triacrylate were dissolved 0.40 g of thefollowing copolymer, 6.00 g of Pargascript Red I-6-B (tradename ofCiba-Geigy) and 2 g of Emulex NP-8 (tradename of Nippon Emulsion Co.,Ltd.). ##STR1##

In 18.00 g of the solution was dissolved 0.002 g of the following thiolderivative. ##STR2##

To the resulting solution was added a solution in which 0.16 g of thefollowing reducing agent (I) and 1.22 g of the following reducing agent(II) are dissolved in 1.80 g of methylene chloride.

The pKa value of the reducing agent (I) is 13.9, and the pKa value ofthe recuding agent (II) is 10.8, wherein the values were measured by acomplex glass electrode containing saturated methanol solution ofpotassium chloride as an internal solution under the followingconditions.

Solvent: Dimethylformamide (DMF)

Supporting electroylte: (CH₃)₄ NBF₄

Concentration of reducing agent: 0.005 M

Titrant: 10% Methanol solution of (C₄ H₉)₄ NOH ##STR3##

To the resulting solution were added 3.50 g of the silver halideemulsion and 3.35 g of the silver benzotriazole emulsion, and themixture was stirred at 15,000 r.p.m. for 5 minutes to obtain alight-sensitive composition.

Preparation of light-sensitive microcapsule

To 10.51 g of 18.6% aqueous solution of Isobam (tradename of KurarayCo., Ltd.) was added 48.56 g of 2.89% aqueous solution of pectin. Afterthe solution was adjusted to a pH of 4.0 using 10% sulfuric acid, thelight-sensitive composition was added to the resulting solution, and themixture was stirred at 7,000 r.p.m. for 2 min. to emulsify thelight-sensitive composition in the aqueous medium.

To 72.5 g of the aqueous emulsion were added 8.32 g 20 of 40% aqueoussolution of urea, 2.82 g of 11.3% aqueous solution of resorcinol, 8.56 gof 37% aqueous solution of formaldehyde, and 2.74 g of 8.76% aqueoussolution of ammonium sulfate in this order, and the mixture was heatedat 60° C. for 2 hours while stirring. After the mixture was adjusted toa pH of 7.0 using 10% aqueous solution of sodium hydroxide, 3.62 g of30.9% aqueous solution of sodium hydrogen sulfite was added to themixture. Further, the mixture was adjusted to a pH of 5.0 using 10%sulfuric acid to obtain a dispersion containing light-sensitivemicrocapsules.

Preparation of light-sensitive material

To 10.0 g of the light-sensitive microcapsule dispersion were added 10 gof 1% aqueous solution of the following anionic surfactant and 1.0 g of10% solution (solvent: water/ethanol =50/50 as volume ratio) ofguanidine trichrolacetate to prepare a coating solution. ##STR4##

The coating solution was uniformly coated on a polyethyleneterephthalate film (thickness: 100 μm) using a coating rod of #40 togive a layer having a wet thickness of 70 μm and dried at about 40° C.to obtain a light-sensitive material (A).

The pH value of the light-sensitive layer was 5.2, wherein the value wasmeasured by the process comprising: dropwise adding distilled water onthe light-sensitive layer; applying Horiba Flat Glass Electrode(tradename of Horiba Seisakusho Co.l, Ltd.) on the area wetted bydistilled water in the light-sensitive layer to connect the glasselectrode with the layer via water; and measuring the value after 30seconds by Horiba pH meter F-7AD (tradename of Horiba Seisakusho Co.,Ltd.)

EXAMPLE 2

Preparation of light-sensitive microcapsule

The dispersion containing light-sensitive microcapsules was prepared inthe same manner as in Example 1, except that the mixture was adjusted toa pH of 6.0 using 10% sulfuric acid at the last pH-adjustment.

Preparation of light-sensitive material

The light-sensitive material (B) was prepared in the same manner as inExample 1, except that the above light-sensitive microcapsule dispersionwas used.

The pH value of the light-sensitive layer was 6.2, wherein the value wasmeasured in the same manner as in Example 1.

COMPARISON EXAMPLE 1 Preparation of light-sensitive microcapsule

To 10.51 g of 18.6% aqueous solution of Isobam (tradename of KurarayCo., Ltd.) was added 48.56 g of 2.89% aqueous solution of pectin. Afterthe solution was adjusted to a pH of 4.09 using 10% sulfuric acid, thelight-sensitive composition used in Example 1 was added to the resultingsolution, and the mixture was stirred at 7,000 r.p.m. for 2 min. toemulsify the light-sensitive composition in the aqueous medium.

To 72.5 g of the aqueous emulsion were added 8.32 g of 40% aqueoussolution of urea, 2.82 g of 11.3% aqueous solution of resorcinol, 8.56 gof 37% aqueous solution of formaldehyde, and 2.74 g of 8.76% aqueoussolution of ammonium sulfate in this order, and the mixture was heatedat 60° C. for 2 hours while stirring. After the mixture was adjusted toa pH of 7.0 using 10% aqueous solution of sodium hydroxide, 3.62 g of30.9% aqueous solution of sodium hydrogen sulfite was added to themixture to obtain a dispersion containing light-sensitive microcapsules.

Preparation of light-sensitive material

The light-sensitive material (C) was prepared in the same manner as inExample 1, except that the above light-sensitive microcapsule dispersionwas used.

The pH value of the light-sensitive layer was 7.2, wherein the value wasmeasured in the same manner as in Example 1.

COMPARISON EXAMPLE 2 Preparation of light-sensitive microcapsule

The dispersion containing light-sensitive microcapsules was prepared inthe same manner as in Comparison Example 1, except that the mixture wasadjusted to a pH of 8.0 using using 10% aqueous solution of sodiumhydroxide at the last pH-adjustment.

Preparation of light-sensitive material

The light-sensitive material (D) was prepared in the same manner as inExample 1, except that the above light-sensitive microcapsule dispersionwas used.

The pH value of the light-sensitive layer was 8.1, wherein the value wasmeasured in the same manner as in Example 1.

Preparation of image-receiving material

To 150 g of water was added 11 g of 40% aqueous solution of sodiumhexametaphosphate, and were further added 34 g of zinc3,5-di-α-methylbenzylsalicylate and 82 g of 55% slurry of calciumcarbonate, followed by coarsely dispersing in a mixer. The coarsedispersion was then finely dispersed in Dynomill dispersing device. To200 g of the resulting dispersion were added 6 g of 50% latex of SBR(styrene-butdiene rubber) and 55 g of 8% aqueous solution of polyvinylalcohol, and the resulting mixture was made uniform.

The mixture was then uniformly coated on an art paper having a basisweight of 43 g/m² to give a layer having a wet thickness of 30 μm anddried to obtain an image-receiving material.

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Examples 1 & 2 andComparison Examples 1 & 2 was exposed to light all over thelight-sensitive layer using a tungsten lamp at 200 lux for 1 second, andthen heated on a hot plate at 125° C. for 40 seconds. The exposed andheated light-sensitive material was then combined with theimage-receiving material and passed through press rolls under pressureof 350 kg/cm². The density of the formed color on the image-receivingmaterial was measured using Macbeth reflection densitometer.

Further, each of the light-sensitive materials was evaluated asmentioned above, except that each of the materials was not exposed tolight.

Furthermore, each of the light-sensitive materials was preserved in athermostat at 50° C. for 1 day, and then evaluated after the exposure orwithout the exposure as mentioned above.

The results are set forth in Table 1.

In Table 1, "Dmin" means the density of the formed color when theexposed light-sensitive material was used (corresponding to the exposedarea), and "Dmax" means the density when the unexposed material is used(corresponding to the unexposed area).

                  TABLE 1                                                         ______________________________________                                        Light  pH Value of Immediately  One Day Storage                               Sensitive                                                                            Light-Sensi-                                                                              (after Preparation)                                        Material                                                                             tive Layer  Dmim    Dmax   Dmim  Dmax                                  ______________________________________                                        (A)    5.2         0.07    1.30   0.07  1.30                                  (B)    6.2         0.08    1.29   0.08  1.29                                  (C)    7.2         0.08    1.29   0.42  1.29                                  (D)    8.1         0.07    1.30   0.86  1.30                                  ______________________________________                                    

It is apparent from the results in Table 1 that each of thelight-sensitive materials (A) and (B) gives an improved positive imagehaving a low minimum density (Dmin) even if it has been preserved undera severe condition.

EXAMPLE 3 Preparation of light-sensitive material

To 10.0 g of the light-sensitive microcapsule dispersion prepared inExample 1 was added 1.0 g of 1% aqueous solution of the anionicsurfactant used in Example 1 to prepare a coating solution. The coatingsolution was uniformly coated on a polyethylene terephthalate film(thickness: 100 μm) using a coating rod of #40 to give a layer having awet thickness of 70 μm and dried at about 40° C. to obtain alight-sensitive material (E).

The pH value of the light-sensitive layer was 5.2, wherein the value wasmeasured in the same manner as in Example 1.

EXAMPLE 4 Preparation of light-sensitive material

The light-sensitive material (F) was prepared in the same manner as inExample 3, except that 10.0 g of the light-sensitive microcapsuledispersion prepared in Example 2 was used.

The pH value of the light-sensitive layer was 6.2, wherein the value wasmeasured in the same manner as in Example 1.

COMPARISON EXAMPLE 3 Preparation of light-sensitive material

The light-sensitive material (G) was prepared in the same manner as inExample 3, except that 10.0 g of the light-sensitive microcapsuledispersion prepared in Comparison Example 1 was used.

The pH value of the light-sensitive layer was 7.2, wherein the value wasmeasured in the same manner as in Example 1.

COMPARISON EXAMPLE 4 Preparation of light-sensitive material

The light-sensitive material (H) was prepared in the same manner as inExample 3, except that 10.0 g of the light-sensitive microcapsuledispersion prepared in Comparison Example 1 was used.

The pH value of the light-sensitive layer was 8.1, wherein the value wasmeasured in the same manner as in Example 1.

Preparation of sheet containing base

To 10 g of water were added 4.2 g of 10% aqueous solution of gelatin,2.8 g of 10% aqueous solution of sodium hydrogencarbonate and 1.0 g of1% aqueous solution of the anionic surfactant used in Example 1 toprepare a coating solution. The coatin solution was coated on apolyethylene terephthalate film (thickness: 100 μm) using a coating rodof #40 to give a layer having a wat thickness of 70 μm and dried atabout 40° C. to obtain a sheet containing a base (base sheet).

Evaluation of light-sensitive material

Each of the light-sensitive materials prepared in Examples 3 & 4 andComparison Examples 3 & 4 was exposed to light all over thelight-sensitive layer using a tungsten lamp at 200 lux for 1 second, andthen pressed on the base sheet which had been wetted by water. After thebase sheet was removed, each of the light-sensitive material was heatedon a hot plate at 125° C. for 40 seconds. The exposed and heatedlight-sensitive material was then combined with the image-receivingmaterial and passed through press rolls under pressure of 350 kg/cm².The density of the formed color on the image-receiving material wasmeasured using Macbeth reflection densitometer.

Further, each of the light-sensitive materials was evaluated asmentioned above, except that each of the materials was not exposed tolight.

Furthermore, each of the light-sensitive materials was preserved in athermostat at 50° C. for 1 day, and then evaluated after the exposure orwithout the exposure as mentioned above.

The results are set forth in Table 2.

In Table 2, "Dmin" and "Dmax" have the same means in Table 1.

                  TABLE 2                                                         ______________________________________                                        Light  pH Value of Immediately  One day Storage                               Sensitive                                                                            Light-Sensi (after Preparation)                                        Material                                                                             tive Layer  Dmin    Dmax   Dmin  Dmax                                  ______________________________________                                        (E)    5.2         0.07    1.30   0.07  1.30                                  (F)    6.2         0.08    1.29   0.08  1.30                                  (G)    7.2         0.08    1.29   0.60  1.29                                  (H)    8.1         0.07    1.30   1.10  1.30                                  ______________________________________                                    

It is apparent from the results in Table 2 that each of thelight-sensitive materials (E) and (F) gives an improved positive imagehaving a low minimum density (Dmin) even if it has been preserved undera severe condition.

I claim:
 1. A light-sensitive material comprising a light-sensitivelayer which contains silver halide grains, a reducing agent and anethylenic unsaturated polymerizable compound provided on a support, saidsilver halide grains and polymerizable compound being contained inmicrocapsules which are dispersed in the light-sensitive layer, whereinthe light-sensitive layer has a pH value of not higher than
 7. 2. Thelight-sensitive material as claimed in claim 1, wherein thelight-sensitive layer has a pH value of from 5 to 6.5.
 3. Thelight-sensitive material as claimed in claim 1, wherein thelight-sensitive layer further contains an acid.
 4. The light-sensitivematerial as claimed in claim 1, wherein the light-sensitive layerfurther contains an inorganic acid.
 5. The light-sensitive material asclaimed in claim 1, wherein the light-sensitive layer further containsan acid having a boiling point of 80° to 200° C.
 6. The light-sensitivematerial as claimed in claim 1, wherein the light-sensitive layerfurther contains a color image forming substance.
 7. The light-sensitivematerial as claimed in claim 1, wherein the reducing agent is containedin the microcapsules.
 8. The light-sensitive material as claimed inclaim 1, wherein the reducing agent has a pKa value of not lower than 9.9. The light-sensitive material as claimed in claim 1, wherein thelight-sensitive layer further contains a binder.
 10. An image formingmethod which comprises the steps of:imagewise exposing a light-sensitivematerial comprising a light-sensitive layer which contains silver halidegrains, a reducing agent and an ethylenic unsaturated polymerizablecompound provided on a support, wherein the light-sensitive layer has apH value of not higher than 7; raising the pH value of thelight-sensitive layer to a value of higher than 7; and simultaneously orthereafter heating the light-sensitive material to imagewise polymerizethe polymerizable compound.
 11. The image-forming method as claimed inclaim 10, wherein the silver halide grains and polymerizable compoundare contained in microcapsules which are dispersed in thelight-sensitive layer.
 12. The image-forming method as claimed in claim10, wherein the light-sensitive layer has a pH value of from 5 to 6.5.13. The image-forming method as claimed in claim 10, the light-sensitivematerial is heated at an a temperature in the range of 80° to 200° C.14. The image-forming method as claimed in claim 10, wherein afterheating the light-sensitive material, the light-sensitive material ispressed on an image-receiving material to transfer the unpolymerizedpolymerizable compound to the image-receiving material.